The present invention relates generally to actuator mechanisms and more particularly concerns an actuator mechanism which will move a controlled member to a predetermined position in response to predetermined conditions. The invention will be described by way of example, in connection with a mechanism with a fusible or meltable link that rotates a valving member to a fail-safe position in response to a fire or other ultra high temperature conditions.
Many industrial facilities have controlled mechanisms that must be moved to a predetermined position upon the occurrence of certain contingencies. One such example would be a valve in a hydrocarbon process line. Since the hydrocarbon media in the process line controlled by such a valve is flammable, it may be highly desirable to move the valve to a closed position in order to terminate the hydrocarbon flow in the event of a fire. In such a situation, the failure to move the valve may result in feeding the fire and compounding any resulting dangers and damages.
Conversely, the line may contain a fire extinguishing agent, the flow of which would be highly desirable under fire conditions. The preferred position for a valve controlling such a media would be in an open position, a position which would allow discharge of the fire repellant and serve to extinguish the fire.
Unfortunately, fire and other ultra high temperature conditions often destroy valve actuating mechanisms and controls therefore. Alternately, the valve may be manually operated and inaccessible in case of fire. Consequently, it is possible that a particular valve or other type of mechanism will be in an undesirable position in a fire situation and an operator will be unable to control the valve to move it to the more desirable position.
In order to overcome the problem described above, certain "fail-safe" actuators have been developed to return a valve member to its preferred position in response to certain conditions. One such example is disclosed in U.S. Pat. No. 4,275,642. In that patent, a disparity in exhaust air flow resistances on opposite sides of an air actuated vane type actuator causes a valve to move to a preferred position in the event of a sudden drop in air pressure.
The present invention, in its preferred form, is responsive to temperature to move a valve or other controlled device to a preferred position in the event of a fire. A fusible material which will melt under fire conditions is used to support a load induced by a stored energy device. When the fusible material is melted under high temperature conditions, the fusible material will no longer support the load induced by the stored energy device, and the stored energy in that device is used to move the controlled device to its preferred position.
It is therefore an object of the present invention to provide an actuator that will move a controlled mechanism to a predetermined position in response to high temperature conditions.
It is another object of the present invention to provide an actuator which will store energy and release that stored energy in response to high temperature conditions.
It is yet another object of the present invention to provide an actuator which will hold a controlled mechanism in a predetermined position after having moved the controlled mechanism to that predetermined position.
It is still another object of the present invention to provide an actuator that will move a controlled member to a predetermined position that may be adjusted.